Earthship power consumption July 2008

We used 1407 kWh this month, up from our run of low months. This is because of the dryer. My allergies were severe, so I washed everything (curtains, rugs, mattress covers, pillows, etc.). And I used the dryer to catch all the lint. What I found: TONS of pet hair. I'm glad I don't have carpet.

This chart is from the May 2006 - present earthship power usage history spreadsheet. You can also read the post that explains our power fluctuations over the course of a year.

Power usage March, April, May 2008

It is June and 87 degrees as I write this. My A/C is on. A lot. So I am curious to see what happens this summer. Last year, we began running our A/C in May. This year, we think due to the green roof and its insulation properties, we got four more weeks before we had to start running the air.

I am not 100% sure what all the differences are in these two years, but our power consumption dropped significantly compared to the same months last year. Things like line drying clothes, eliminating the power drain of the rainwater harvesting system, and significant improvement to the insulation of the ceiling (thanks again to the green roof) all played a role. We also intermittently turn off our electric hot water backup and rely exclusively on the solar hot water, especially in the heat of the summer. We are consistently hitting our goal of 1,000 kWh or less per month and have not sacrificed quality of life; we use a dishwasher, clothes washer, have nice hot water, computers, lights, etc.

March
2007: 1531
2008: 884

April
2007: 1658
2008: 754

May
2007: 975
2008: 615

Earthship power usage Feb 2008: 1044 kWh

We've been running our electric heat since our firewood is too wet this year, and this habit is reflected in our power usage this month. Still, we are very close to 1,000 kWh. Also, our housekeeper brings and uses a vacuum cleaner (something we never did before) and that may have increased our usage, too.

Our six month usage history is:

• Feb 2008 1044
• Jan 2008 904
• Dec 2007 642
• Oct 2007 675
• Nov 2007 818
• Sep 2007 1254

Power usage Jan 2008: 905 kWh

Part of making the kWh number meaningful is knowing what it represents. In this case, our 904 kWh includes:

• Using the heating function of our multi-splits for about 15 hours total over the month
• Washing clothing for 4 in a washing machine
• Drying whites only in the dryer, everything else goes on the line
• 2 computers, on most during most of every day (but not night)
• Regular use of the electric stove, tea kettle, microwave, and hot water heater (although our hot water is greatly supplemented by our solar hot water heater, even in the winter)

Fujitsu multi-split units: effects of use on power consumption

How much energy do Fujitsu multi-split units use in a real-life setting? Apparently, not very much. Our last 30 days of power use was 642 kWh and we used our Fujitsu multi-split units for heating our 1,600 SF interior . The heat they provided was dry and warm, not like heat-pump heat I have experienced in the past.

We never planned to have electric heat. We have Bert, our wood stove, who does duty as a heater, light source, marshmallow toaster, home scent diffuser, and soil additive manufacturer. As with most people living in a bermed home, we noticed that the winter temperature rose dramatically in the first three years, settling out to an unheated dawn temperature of 17(63). The first winters saw lower temps, more like 14(57). So Bert's job duties shifted from being significant heat source to chasing off the damp chill of a mild Southern winter. Whatever we wanted to use Bert for, Bert ate wood.

On a very wet cold day, we would go through 10 pieces of wood in a 24 hour period. Usually, we would light a fire 3, maybe 4, times a week at most. Remember, a sunny day brings the temperature in our house up to a balmy 25(77). A cord of wood lasts us about 3 years. Firewood needs to age in order to catch quickly. Aged too much, it is called mulch. Aged not enough, it is called why-won't-this-fucking-fire-start. The trick to properly aging firewood is a tarp that covers the top and protects the wood from water and sun. No tarp, and in a short 18 months you'll have a wood-pile shaped lump of mulch and bugs. Fresh wood won't start. We've found that wood needs 1 year to start with aggressive assistance. At two years, it will start with little assistance. At the three year mark you can light it, literally, with a match.

This year, we have a cord of fresh wood. The why-won't-this-fucking-fire start kind, seeing as it was cut down about 8 weeks ago. We used the old logs as starter logs, and by putting the new wood onto a bed of glowing coals even the greenest of logs could not refuse to ignite. We used up the last bits of match-light firewood last month. And being low-work people, have not really had a fire since.

A lightening strike took out our old A/C only unit a few months ago. That unit is no longer maid, and the new model included a heating function. There is one outdoor unit and three indoor units: one in the main room, one in the kids' area, and one in our bedroom. We are using them separately for a few hours each day. First thing in the morning, the temperature is a perfect 21(70) in the great room, but feels damp and chilly. We've noticed that temperature alone is not a good way of measuring how cold it feels. Humidity and pressure play a mysterious role perception of "cold."

The splits let us decide where and when to apply heat. This morning, I have the great room unit on, and nothing else. I will turn it off around 10, when the greenhouse is warming up. In the evening, I'll turn on the ones in the bedrooms for 2 hours, and then shut them off when we go to sleep. This level of electric heating has not significantly increased our power consumption. Isn't that weird?

Last month, we used 675kWh. This month, with the addition of the splits, we used 642kWh. Does this mean the multi splits use less energy to heat our home than our dryer does to dry our clothes? Could a standard house heat itself with so little use of the units? Maybe the energy savings is just a function of the insulation... none of the heat gets out, so we use less of it. It could even be the green roof, or maybe a combination of all of these things. I am looking forward to more data that can help me understand what is going on.

Another record low power usage month: 675 kWh

We have not seen numbers this low since we first moved in. But back then, it was ROUGH here at the ship. The floor was newly cured, bare concrete. The berm was not in place. Not all the windows were completely framed in, so there were a lot of bugs. There was no floor or ceiling in the greenhouse. We did not have a washer or dryer or dishwasher.

The first winter here, our low temperature was 55. We used space heaters. The first summer, our high temperature was 110. We spent the days at the YMCA pool. It was like camping in a lien-to during the winter and living in a solar oven during the summer.

Now, we are living very comfortably. Our winter low is 66, summer high is 80. We have a tile in the house, brick in (almost) all of the greenhouse, and no bugs. We have a dishwasher and a clothes washer. The house feels like a comfortable house vs. an uncomfortable camp ground. But does not use any more energy than it did when we were roughing it.

Power use history
Nov 06 1319
Dec 06 1567
Jan 07 1598
Feb 07 1529
Mar 07 1531
Apr 07 1658
May 07 975
Jun 07 1250
Jul 07 1576
Aug 07 1535
Sep 07 1254
Oct 07 818
Nov 07 675

Power consumption hits new low: 818 kWh

Our last 29 days of consumption (September 2007) is a skinny 818 kWh.

We are thrilled! Our clothes line took us the rest of the way toward our goal. Apparently, our dryer uses almost 400 kWh per month. We've been using the A/C regularly in the past 29 days and still were able to keep under 1,000. The cooler months ahead have historically been our low-consumption months since there is no electric central heat. Most of our heat comes from the low winter sun that pours in through the southern glass wall each day. We supplement the passive solar heat with a wood burning stove on occasion. Since we made it through an A/C using month at under 1,000 kWh, we may have hit our goal much sooner than we expected. Is it too early for champagne?

Installing a solar dryer

We cleared a 20' stretch of wall in the greenhouse and installed a laundry line against the wall. Hanging clothes out to dry does not get any easier than this. Always inside, always warm, and often intensely sunny, the greenhouse is the perfect spot. We used off-the-shelf products and made it very easy to use- its at just the right height for me, smooth pulley action, and a work surface underneath. It will be another few weeks before we see how much power this is saving us.

We had to drill 2 holes for this project- the rest of the pieces just snap together. Meanwhile, I am enjoying the experience of hanging the laundry. I no longer have to remember to keep my bras out of the dryer. I have not bought dryer sheets. My clothes had a different smell: clean vs. perfumed. My t-shirts are not too tight when I first put them on. Cons are that the jeans lean towards crunchy and dry time is 12 hours, give or take. Staying on top of it with small loads each day seems to be working for us. Our first load was too big for the line and I ended up hanging socks and linens on chairs in the greenhouse. I started washing slightly smaller loads. An unexpected bonus is that my son can rig his Bionicles onto the line and zip them around.

Power usage: June - September 2007

Our A/C unit was struck by lightening and had to be replaced. Apparently, our area is a hot bed of lightening strikes due to the magnetic properties of Lake Drummond in the Great Dismal Swamp . Who knew? We had to have it replaced. The small (6 ton) unit we originally purchased is no longer made and we went with the smallest multi-split unit currently available: 10 tons. The A/C works great. The interior temperature is now consistently 79 degrees. We often leave the units off at night. It is also proving to be more efficient because even though the house is much cooler, our power usage is staying constant. Inspiring. Our current numbers show us that we are approximately 500 kWh away from our goal of 1,000 kWh per month. A clothes line just might do the trick. We could set it up in the greenhouse, which would help increase the humidity there. Hmmmm. I think I feel a project coming on.

June 2007 1250 kWh
July 2007 1576 kWh
August 2007 1535 kWh
September 2007 1254 kWh

Effects of well usage on power consumption

Our power usage for this billing period was 1250kWH. We have been running the A/C for most of this billing period, but have eliminated power draws associated with rainwater harvesting: sand filter and UV light. Both systems require a pump, but the pump in our well which is slightly more efficient than the pump that was used to draw rainwater from the cisterns.

Over all, when we compare this month to a month of full A/C and rainwater (vs. well water), our consumption is down by almost 800 kWh. Could it be that the sand filter and UV light used that much power? We may have also underestimated the effect of turning off our electric hot water heater. For almost 2 months now we have been using the solar hot water heater exclusively. Well, we had one rainy day where we turned it on to get the kids de-muddied for a party. But mostly, it has been off.

We have to consider all of these pieces because the power use for this month was MUCH lower than we had expected it to be. We had estimated around 2300 kWh, but only used 1250. Not too shabby. Another variable to consider is our dishwasher. We had one installed about 4 weeks ago. We've read that dishwashers actually use less water and power because they are so much more efficient than human washers. We have ours set for "air dry," only run it when it is packed full to the brim, and use "standard wash." We also spent the extra few dollars to get a stainless steel tub rather than a plastic tub.

The power usage for this month is very inspiring. We had significant A/C usage and a dishwasher and were only 250 kWh over our energy budget. Is this a fluke? Will we use less power this summer vs. last summer? Stay tuned...

Dealing with southern summer heat in an earthship

Our ship, without A/C is bloody HOT. We have had temperatures over 100 degrees. Our particular construction has some flaws that increase the heat: black roof and limited attic-space insulation. Apparently though, ships built in the traditional manner also have summer over-heating issues. We've been in contact with other shippers who also report excessively high temperatures in the summer.

To deal with the heat, we started with reflective coating on the glass in the greenhouse. That did nothing for the temperatures. Then we installed a green house exhaust fan. That reduced the greenhouse temperature to no hotter than it was outside any given day. Before the fan, the greenhouse regularly got up to 120 degrees. We had spider mites, dying plants, and a very stuffy space until the fan was installed. Still, the inside temperature was reaching 100 on a regular basis. Next was shade.

We installed dark curtains to keep the sun out of the main house. This had a slight effect, bringing the interior temperatures down into the high 90's. We were still sweltering most of the time. Finally, we installed A/C. It was a difficult decision and felt like a failure at first.

We opted for low power use units, called Multi Splits, rather than central air. Our A/C is excellent at reducing humidity and the stickiness is more uncomfortable than the heat. Our A/C can effectively reduce the heat by 10 degrees, no more. So, on the hottest 100 degree summer days, the house gets up into the high 80's but is not at all humid. As soon as the sun sets, the house gets comfortable again. We've discovered that anything under 80 is comfortable. Over 80 and we all get... stinky and sticky. But only for a few hours each day.

A year of earthship power consumption data (May 2006-May 2007)

View this information in graph format

May 06: 0643 kWh: This is our lowest power usage point. It represents a time when there was no A/C in the house, we did our laundry off-site, and we had not installed a sand filter to deal with algae in the rainwater. It includes the greenhouse exhaust fan, UV light, electric backup hot water, 2 computers, a PS2, electric range, microwave, and rainwater pump. We use this number, 643, as our "base line" measure when determining how much other luxuries cost in terms of kWh. By keeping to 1,000 kWh we can live on the energy generated by small-sized solar array. Bear in mind that said array runs about $25,000 and we have not installed it to date.

Jun 06: 1216 kWh: The A/C was installed mid-month.

Jul 06: 2067 kWh: A full month of A/C added approximately 1400 kWh.

Aug 06: 2387 kWh: The hottest month. We were even gone for 7 days of this month, and left the A/C off. It was still our highest usage point.

Sep 06: 2346 kWh: No changes.

Oct 06: 1607 kWh: We stopped using the A/C towards the end of this month, but we installed the sand filter. We also installed a washer and dryer this month.

Nov 06: 1319 kWh: No A/C this month. Using May 06 as a bench mark, we estimate that the sand filter and the dryer each use approximately 330 kWh per month.

Dec 06: 1567 kWh: We cannot explain the increase this month. Maybe the electric hot water heater uses more in the cold months.

Jan 07: 1598 kWh: We cannot explain the increase this month, but are still eyeing the hot water heater.

Feb 07: 1529 kWh: No changes.

Mar 07: 1531 kWh: No changes.

Apr 07: 1658 kWh: No changes.

May 07: 0975 kWh: The sand filter has been disconnected. This means that our earlier estimate that the sand filter uses up approximately 300 kWh per month was very accurate. For June, we have disconnected the electric hot water and are using solar heated water only. We have also eliminated the UV light. We'll be using the A/C in another few weeks, to the tune of an additional 1400 kWh. That puts us 1375 kWh over our energy budget. Where can we cut more?

View this information in graph format

Earthship switches to a shallow well for drinking water

Can you hear that? Neither can we. What we cannot hear is the noise of the pressure tank and motor. The pressure tank and motor used to be inside the house, in the utility area. We dared not flush in the night for fear of walking up our young son. For the last few nights we've been night-flushing with reckless abandon. The other thing we do not hear is the sound of our power meter spinning so much; the shallow well uses far less electricity than our rainwater harvesting system did.

We eliminated a sand filer (this could also have been eliminated with black tanks, but a circulation pump is necessary either way), 2 in-line filters, and a UV light. Overall, we feel we are getting better water (no chemical drift from fertilized crops next door) with a smaller carbon footprint. If we had it to do over... I would probably get a shallow well to begin with and structure the house for a 9-12" sod roof. Rainwater collection for use as potable water was too complicated for our application and did not address water safety to my satisfaction. Collecting rainwater for irrigation is viable and works for us. If the health department was not insistent on potable water being in the toilets, I would use rainwater for flushing. But according to our codes, ALL exposed water (even the stuff in the bowl) must be drinkable.